This invention relates to refrigeration systems used for air conditioners or the like.
The refrigeration system of this kind usually has a main circuit 5 as shown in FIG. 1, including a compressor 1, a condenser 2, a capillary tube 3 and an evaporator 4, these parts being connected in the order mentioned. In this main circuit 5, a high temperature, high pressure coolant gas, having been compressed in the compressor 1, is fed into the condenser 2, and the liquid coolant liquefied in the condenser 2 is fed, after being expanded by pressure reduction in the capillary tube 3, to the evaporator 4. As the liquid coolant is evaporated in the evaporator 4, the ambient air is cooled. In order to bypass part of the coolant fed out from the condenser 2 in the main circuit 5 to the low pressure side of the compressor, a bypass circuit 8 including an electromagnetic valve 6 and an auxiliary capillary tube 7 is connected between the low pressure side of the compressor 1 and the high pressure side thereof. Further, between the condenser 2 and capillary tube 3 of the main circuit 5 there are provided a circuit breaker switch 9 and a bypass switch 10, these switches being sensitive for their operation to the pressure of the coolant. The circuit breaker switch 9 functions to disconnect the main circuit 5 to stop an air conditioner or the like when a first preset pressure P1 (for example, 26 kg/cm.sup.2) is reached by the pressure of the coolant. The bypass switch 10 acts to open the electromagnetic valve 6 when a second preset pressure P2 (for example, 22 kg/cm.sup.2) lower than the aforementioned first preset pressure P1 is reached by the pressure of the coolant. Thus, when the pressure of the coolant gas being compressed by the compressor 1 is increased, the electromagnetic valve 6 is opened to let part of the liquid coolant having been fed out from the condenser 2 to be bypassed through the bypass circuit 8 so as to prevent overcooling by the evaporator 4.
With the prior art refrigeration system as described above, when the electromagnetic valve 6 is opened with the bypass switch 10 turned on in response to the reaching of the second preset pressure P2 by the pressure of the coolant passing through the main circuit 5, part of the liquid coolant fed out from the condenser 2 is caused to rush into the bypass circuit 8. Consequently, immediately after the instant T of opening of the electromagnetic valve 6 the pressure of the coolant is temporarily reduced as shown in FIG. 2. However, since the rate of flow of the coolant into the bypass circuit 8 is limited, the coolant which is not admitted into the bypass circuit 8 is temporarily retained in the neighborhood of the inlet of the bypass circuit 8, thus resulting in a sharp increase of the pressure of the coolant. After the lapse of about 0.5 second from the opening of the electromagnetic valve 6, the pressure of the coolant exceeds the first preset pressure P1. Therefore, the circuit breaker switch 9 is turned on so that the air conditioner is unnecessarily stopped. To preclude such deficiency, it is necessary to set the pressure difference between the first and second preset pressures to a comparatively large value for preventing the air conditioner from being stopped due to a transient pressure increase as mentioned above.